A trial of capivasertib with docetaxel for prostate cancer that has spread (ProCAID)

The trial team didn’t find that adding capivasertib improved treatment. It didn’t increase the length of time before the cancer started to grow again. But the side effects were manageable. 

Trial design
150 people took part in this phase 2 trial. 

There were 2 treatment groups. People were put into a group at random:

• 75 had docetaxel, prednisolone and capivasertib
• 75 had docetaxel, prednisolone and a dummy drug 

Diagram 1

Neither the men nor their doctor could choose which group they were in. And neither of them knew which group they were in. This is called a double blind trial.

Everyone had treatment in cycles. Each 3 week period was a cycle of treatment . They had:

• docetaxel and prednisolone for up to 10 cycles
• capivasertib or the dummy drug for as long as treatment was working and the side effects weren’t too bad

Results
The trial team looked to see how well treatment worked. They looked at how long it was before the cancer started to grow again. This is called progression free survival. They found it was:

• just over 7 months (7.03) for people who had docetaxel, prednisolone and capivasertib
• just under 7 months (6.7) for people who had docetaxel, prednisolone and the dummy drug 

So the team found that adding capivasertib didn’t increase the length of time before the cancer started to grow again. 

The trial team also looked at how long people lived. They found that this was about:

• 31 months for the people who had docetaxel, prednisolone and capivasertib
• 20 months for the people who had docetaxel, prednisolone and the dummy drug 

So the trial found that people in the capivasertib group lived about 11 months longer. This isn’t what the team had expected. They aren’t sure why people who had capivasertib lead to an increase in the time people lived. But it didn’t extend the length of time before the cancer started to grow again.  

The team say the data from the trial doesn’t provide a clear explanation for why this happened. They think it is possible that these results may be false. There might have been some bias  within the trial design that they weren’t fully aware of. 

Some differences between the people in each group may have favoured the capivasertib group. There may have been a number of reasons for this. For example people in the capivasertib group may have had lower rates of cancer spread in the liver or lung. 

Tissue and blood samples 
The trial team looked at the blood and tissue samples (biopsies ) the men gave as part of their routine diagnosis. They wanted to see if their cancer cells had changes (mutations)  in any of the following genes:

• PIK3CA
• AKT1
• PTEN

The team had this information for 136 people. Of those:

• 44 had the gene changes
• 92 didn’t have the gene changes

The team thought that capivasertib would work better in those who had the gene changes. But the team found no link between this and how well treatment worked in either group. 

Side effects
The team looked at the number of bad to severe side effects. There were a similar number in both treatment groups. 

The most common related to capivasertib were:

• diarrhoea
• tiredness (fatigue)
• feeling sick
• skin rash

The team found the side effects were manageable. 

Conclusion
The trial team concluded that adding capivasertib to chemotherapy didn’t work for people with advanced prostate cancer. It didn’t increase the length of time before the cancer started to grow again. 

Adding capivasertib increased how long people lived. But it is possible that bias may have impacted these results. 

Even so, all trial results help doctors and researchers understand more about different cancers and the best way to treat them. 

Where this information comes from    
We have based this summary on information from the research team. The information they sent us has been reviewed by independent specialists (peer reviewed ) and published in a medical journal. The figures we quote above were provided by the trial team who did the research. We have not analysed the data ourselves.